1. Field of the Invention
The present invention relates generally to vibratory feeders and conveyors, and more particularly to linear non-uniform pulsating motion conveyors.
2. Description of the Related Art
Conventional designs of reciprocating conveyors usually employ electromagnetic drives or motor-driven mechanical drives. An electromagnetic drive utilizes the oscillating magnetic attraction between a magnet armature and a pole face of a magnet. Practical use of the electromagnetic drive requires that the magnet armature be in relative close proximity to be attracted to the pole face of the magnet, putting a severe limitation on the maximum stroke obtainable, usually under 0.1 inches. The design must operate at higher frequencies, about 30 Hz and higher, in order to achieve the accelerations needed to obtain the desired conveying feed rates. Motor driven mechanical drives typically include rotary motors that spin eccentric weights or turn shafts which are connected to cams or crank arms. Mechanical drives convert rotary motion to linear vibratory motion and produce some form of harmonically varying stroke at a set frequency. Mechanical drives generally operate at strokes up to 1 inch, at frequencies ranging from 8 Hz to 20 Hz.
One type of reciprocating vibratory conveyor is known as a differential motion conveyor. This type of conveyor utilizes a motor driven mechanism containing at least two geared shafts with weights of differing eccentricities on each shaft. The mechanism produces a linear reciprocal horizontal motion of the conveying surface that has a lower acceleration and velocity in the forward direction than in its rearward direction. This difference in acceleration and velocity allows the product being conveyed to slip less in the forward direction than when the conveying surface is accelerating in its rearward direction, thus the product moves forward along the conveying surface.
Some conveyors in the prior art use some form of an electromagnetic linear motor as a drive mechanism. There are several examples of electromagnetic linear motors. For example, a voice coil actuator uses a coil located in a magnetic field which exerts a force on the coil when a current is conducted through the coil. Another example is an induction motor, which uses a stator having coils and an armature made of magnetic material, and are typically used as motors for trains and monorails. Induction of currents generated in the armature creates magnetic fields which are either attracted or repulsed by magnetic fields generated by the stator coils. A moving magnet motor is another example, and this motor uses a stator with a plurality of coils which are sequentially energized by a control. An armature carrying permanent magnets is moved in relation to the stator by the energized coils.
Other conveyors of the prior art include electromagnetic, linear-motor-driven differential motion conveyors. However, conveyors in the prior art have been driven by a continuous, substantially homogeneous vibration. This uniform vibration could cause parts to transports to stagnate, instead of being transported as intended. Many conveyors in the prior art are known to be massive in size and relatively immobile. Thus, what is needed is a conveyor that relies on non-uniform pulses, can be driven by a solenoid, and can be easily sized and adapted to different types of machinery.